Low prevalence of plasmid-mediated quinolone resistance in Norwegian and Swedish clinical isolates of Escherichia coli and Klebsiella spp.

Abstract number: P1528

Karah N., Poirel L., Sundquist M., Kahlmeter G., Bengtsson S., Nordmann P., Sundsfjord A., Samuelsen Ø.

Objectives: The objective of this study was to examine the prevalence of the plasmid-mediated resistance genes, qnr and aac(6')-Ib-cr, among Norwegian and Swedish clinical isolates of Escherichia coli and Klebsiella spp. with reduced susceptibility to ciprofloxacin and/or resistance to nalidixic acid.

Methods: 487 isolates of E. coli (n = 326) and Klebsiella spp. (n = 31) from (i) Kronoberg Sweden (n = 352) isolated between 2004–5, (ii) the Norwegian surveillance programme for antimicrobial resistance (NORM) (n = 318) isolated in 2005 and (iii) ESBL- (n = 304) or AmpC-producing (n = 33) isolates from the Norwegian Reference Centre for Detection of Antimicrobial Resistance (K-res) collected between 2003–5, were screened for the presence of qnr and aac(6')-Ib-cr genes by multiplex and single PCRs, respectively. PCR products were confirmed by sequencing and the aac(6')-Ib-cr variant was also identified by BstCI-digestion. The genetic environment of qnrS positive isolates was examined by targeted PCR and sequence analysis. Transfer of qnr to E. coli J53 RifR was examined.

Results: Qnr-like encoding genes were identified in 8/487 isolates (1.6%), five Klebsiella spp. (8.2%) and three E. coli (0.7%). Six isolates were qnrS1 positive; Kronoberg (n = 3), NORM (n = 3), and K-res (n = 3) collections. Two isolates were qnrB positive (qnrB1 and qnrB7-like) in the K-res collection. Interestingly, four qnr positive isolates also harbored the aac(6')-Ib-cr variant. Transfer of the qnrS (n = 3) or qnrB (n = 3) genes to E. coli J53 was obtained using 100 mg/L ampicillin as selection pressure indicating plasmid association and co-transfer with a b-lactamase gene. The genetic surroundings of the qnrS1 gene were similar in the three isolates examined. ISEcl2 (orfB ÄorfA) were detected upstream and Äres, orf259, and orf213 were detected downstream of the qnrS1 gene. However, one of the isolates had a further truncated Äres gene. One isolate also carried the pbp3 and blaLAP-1 genes upstream of the qnrS1 gene. The aac(6')-Ib gene was detected in 76/487 isolates (15.6%). 66 (86.8%) of these were of the aac(6')-Ib-cr variant.

Conclusions: (i) The prevalence of qnr (1.6%) and aac(6')-Ib-cr (13.6%) genes are low in Norwegian and Swedish clinical isolates of E. coli and Klebsiella spp. with reduced susceptibility to fluoroquinolones, as already observed in other European countries. (ii) The genetic context of the qnrS1 gene in three isolates showed similar structures as previously described.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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